Many experts do not consider crawling a milestone anymore because some babies do not ever crawl. They roll, scoot, or creep to get where they want to go. This is a huge accomplishment for baby to parents and it means baby will start exploring and getting around the house with ease.
Most babies will crawl if you give them plenty of time on the floor to learn how to move forward. Some babies will go from rolling to pulling up to stand, and that’s ok. The most important thing is to give them the opportunity to learn by being on the floor.